1. Field of the Invention
The present invention relates to an optical element positioning apparatus suitable for use in an optical equipment having a bending optical system.
2. Description of the Related Art
An image pickup apparatuses is generally demanded to have a telephoto lens or a zoom lens and to have an ability of compactly storing a lens barrel at non-photographing time for ease of handling and transport of the image pickup apparatus.
To this end, some image pickup apparatus has a bending optical system that includes a reflection optical element such as a prism disposed between an object-side lens group attached to an extendable and retractable barrel and an image-side lens group for forming an image on an image pickup element disposed within an apparatus main body.
Another image pickup apparatus with a bending optical system has a lens barrel retractable into an empty space created by moving a reflection optical element to a retract position, so as to store the lens barrel inside a main body of the apparatus.
A film scanner (image pickup apparatus) has also been proposed that includes an optical source for illuminating a film screen, a photoelectric conversion means for fetching a film image, and an image forming optical system for leading the film image to the photoelectric conversion means, which are held by holding means that is movable in a direction perpendicular to a scanning direction of the photoelectric conversion means (see, for example, Japanese Laid-open Patent Publication No. 09-284501).
This image pickup apparatus includes an elastic member (pin spring) disposed between the holding means (carriage) and supporting means (lead screw) that drives and movably supports the holding means. The lead screw is lodged between the carriage and the pin spring, whereby play between the carriage and the lead screw is eliminated, thus making it possible to position the carriage with high accuracy.
With the prior art disclosed in Japanese Laid-open Patent Publication No. 09-284501, the carriage is movable in a state that play in a direction perpendicular to a moving direction of the carriage is reduced by the elastic member, whereby the carriage can be stably held at any desired position in its movable range.
However, in the case of an image pickup apparatus having a bending optical system (e.g., a portable compact digital camera), flexure is generated in, e.g., the lead screw due to the weight of the carriage depending on the orientation of the camera (such as vertical, horizontal, upward, or downward orientation). Specifically, when the camera orientation is changed, the carriage position slightly changes. Thus, even if the above-described prior art is applied to the image pickup apparatus of this type, it is difficult to position a reflection optical element of the image pickup apparatus with high accuracy.